XnView Software

Can I anyhow display IPTC:caption in fullscreen mode on the lower part of the photo?

yes Settings>Info

Use the ">" button in Settings, View, Info . dialog to add the fields you want to see.
Then in view mode, use the i key to toggle the display of info or hide them

OK, many thanks, that works. One problem remains for me: In sone cases I would include URLs in captions. In Goggle WEB albums you can copy and paste these to a browser and in this way, for instance, open a Wikipedia article.

In XnView captions, copy/paste isn't supported, apparently. Is there another way to add URLs to photos?

When caption is displayed, right, we can't copy ...

Is there another way to add URLs to photos?

It seems that this feature is missing
A "user defined" overlay icon would be a great suggestion (Settings, Thumbnails, Overlay icons)

The only workaround I've found is to add an "Edit IPTC button" in the View toolbar
Settings, Interface, Toolbar, select View mode
Select "Edit IPTC" on the right side, and bring it to the left
Then, in view mode, we can click this new button and copy something in "Caption" field

Otherwise , we can add some windows shortcuts near to photos, but it's not a very good solution.

@michel038
Your solution is a fine workaround, but doesn't seem to answer the original question. If I have understood correctly, the OP wanted to see the IPTC caption in the status bar, not in the info popup. IAC, that is what I would like. However, the status bar configuration in "Settings" only has checkboxes for predetermined items and apparently doesn't support adding arbitrary fields. The only thing in the list that looked as though it might be useful is "Embedded comment", but when I enable (or disable) it, I don't see any change in the status bar information. What metadata field is "Embedded comment" supposed to represent? Is this the same comment represented in the "Metadata > Edit comment" dialog?